V4L/DVB (3697): More msp3400 and bttv fixes

- remove obsolete VIDIOC_S_INPUT i2c call in bttv
- translate VIDIOCSFREQ to VIDIOC_S_FREQUENCY in i2c call
- improve muting during carrier scan in msp3400
- don't start scan unless really needed.
- no longer reset chip for msp3400c/d.
- remove v4l2 check in tuner-core (radio stops after using the TV)
- add missing VIDIOC_INT_ strings in v4l2-common.c

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>